Vapor-arc device



E. R. STOEKLE VAPOR ARC DEVI CE Filed May 24, 1918 2 Sheets-Sheet 1 5mum QR 35 WW m1 r 25 Dec. 2% 1926. L612547 E. R. STOEKLE VAPOR ARCDEVICE Filed May 24, 1918 2 Sheets-Sheet 2 Wong Patented 2 8, 1926.

UNITED STATES 1,612,547 PATENT OFFICE.

EBWIN B. STOEKLE, OI MILWAUKEE, WISCONSIN, AS SIGNOR TO THE CUTLER-HAM-IEQ KEG. C0., Ol IILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

VAPOR-ARC DEVICE.

Application filed Kay 24, 1918. Serial No. 286,862.

- This invention relates to vapor are devices and is particularlyapplicable to mercury arc rectifiers.

In vapor are devices utilizing auxiliary anodes for ignitin the arcsthereof, especially in the case 0 well evacuated mercury are devices,extremal high ignition potentials are required. n many instances therequired ignition tential has been such as to uncture the ulbs of thedevices employe In consequence, the field of practical application ofsuch devices has been extreme y limited.

On the other hand, vapor are devices, and particularly mercury arcrectifiers, have characteristics which would render the same veryadvantageous for current control purposes and the present invention hasamong its objects to overcome the aforesaid ignition difliculties and tootherwise adapt such devices for additional uses.

Another object is to provide a vapor arc device which will ignitesubstantially instantaneously with the application of the ignitionpotential.

Another object is to provide a va or arc rectifier which will respond toa su ciently low starting potential to enable starting thereof b closureof the main line switch and which may be continuously subjected to theignition potential to maintain its are at very much lower currents thancan ordinarily be accomplished.

Another object is to provide a readily ignited vapor arc rectifier inwhich the arc may be ignited at different values of the impressedpotential wave for producing rectified current pulses of differentshapes and energy content.

According to the present invention it is proposed to introduce into thearc vessel an inert gas to be ionized by theignition potential wherebythe ignition potential may be greatly reduced and for furtherimprovement it is proposed to provide some highly refractory materialupon the surface of the mercury and in some cases to arrange theauxiliary anode in a novel relation with respect to the main anode andcathode.

' The accompanying drawing illustrates certain embodiments of theinvention which will now be described, it being understood that theinvention is suscwtible of embodiment in various other forms.

. Whereas the In the drawing,

Figure 1 shows schematicall grammatically a half wave recti'ing devicehaving the usual arrangemento electrodes, together with one circuitarrangement for said device;

Figs. 2 to 5 show osc-illograph curves obtained with a rectifier such asshown in Fig. 1

Fig. 6 shows a rectifier with a modified arrangement of electrodes' Fig.7 shows a modification of the device shown in Fig. 6; i

Fig. 8 shows a double wave rectifying device; and,

Fig. 9 shows a motor control system emplo ing certain of the aforesaiddevices.

, eferring to Fig. 1, the same shows a so-called half w'ave rectifiercomprising a glass bulb 1 having therein a well of mercury 2constituting a cathode, a main anode 3 and an auxiliary anode 4, saidbulb to be filled with an inert gas such as argon, neon or helium. Suchinert gases are readily i-onizable and it has been found that thepresence thereof enables ignition of and diathe are between the anode 3and mercury cathode 2 by impressing on the auxiliary anode 4 a muchlower potential than would otherwise be required. Further, it has beenfound that the introduction of such gases at low pressures does notimpair the efliciency of the rectifier as compared with the efliciencyof a gas free rectifier of the mercury arc type.

Also, it is preferred to provide the mercury cathode with a surfacecoating 5 of fine particles of some highly refractory material, such forexample, as alkaline earth oxides, or the rare earth oxides, as oxidesof cerium andthorium, which readily give off electrons when incandescentand which are insoluble in the mercury. This coating is provided toincrease the reliability of the device in starting and to overcome theso-called fatiguing of the device when used intermittentl In ractice ithas been found that a devlce lacking this coating may ignite immediatelyor ma be slow to ignite and that after it has een used intermittentlyfor a short time it must be allowed to remain idle for a considerabletime prior to re-ignition thereof, same device when provided with such acoating will always respond substantially instantaneously and may beused intermittently for long periods without si ns of fatigue. This dierence in action ias not been definitely accounted for but it isbelieved to be largely due to the fact that in the former case the glowresulting from ionization of the gas and vapor tends to spread uniformlyover the surface of the mercury without the production of any clearlydefined hot points to assist the ignition, while in the latter case thecoating when subjected to the ignition potential creates points havingintense electric fields about the same whereby such points are subjectedto an intense positive ion bombardment and become incandescent and emitelectrons to assist the ignition. Also, it is believed that the fatigueof ignition of the ordinary vapor are when used intermittently is due toa temporay displacement from the surface of the mercur of some particleswhich are essential to ignition and that when ,the mercury is coatedwith particles of the character described, such particles if displaced,return to the surface of the mercury in sufiicient quantities to insureready ignition.

As shown, the main anode 3 is connected to one side of a supply circuitL, while the cathode 2 is connected to the opposite side of said circuitthrough a battery 6 representing a load. The auxiliary anode 4 isconnected to the secondary winding of a transformer T which has aprimary winding connected across the supply circuit L and said secondarywinding is also connected to the mercury cathode 2. The transformer Tthus supplies the ignition potential to the auxiliary anode and thecathode as is the usual practice and said transformer should be designedto step up the voltage for the ignition circuit to a value determined bythe product of the distance between the electrodes 2 and 4 and thepressure of the inert gas in the arc vessel. In practice it is desirableto include a capacity 7 in the ignition circuit although the same mightbe omitted.

The device, as above stated, serves as a half wave rectifier and inorder to effect ignition of the main arc at the beginning of thepositive cycle ofthe potential of such arc, it is desirable that theauxiliary anode 1 be supplied with its maximum posltive potential at theinstant when the potential on the anode 3 with respect to the cathode 2is passing from zero value to its positive value. And assuming omissionof the capacity, it is essential to ignition of the main are under theseconditions that the potential between the auxiliary anode and cathode bepositive, when the potential between the main anode and cathode ispositive, or in other words, that the potentials be approximately inphase. Thus since the main arc will not ignite before the ignition .tomove the ignition potential reaches a value sufiicient to start throughthe are, that portion being determined by the point on the A. C. wave atwhich the ignition of the arc takes place. This is illustrated in Fig. 2which is a reproduction of an oscillograph record taken with a devicesuch as shown in Fig. l but with the capacity omitted and with only aslightly inductive high resistance of 6700 ohms. 111 this figure arepresents the ignition potential, curve I; themain arc potential, andcurve 0 the main arc rurrent and said curves show ignition of the arejust before the are potential reaches its positive maximum and in thisconnection it may be mentioned that the introduction of an inductance inthe ignition circuit tends oint still nearer to the positive peak of tiemain are voltage. But when a very large inductance is used in theignition circuit and the polarity of the transformer secondary isreversed, the large lag which is introduced will cause the positivemaximum of the ignition potential to occur near the zero value of themain are potential with the results depicted in Fig. 3. In this figure,the curves are lettered as in Fig. 2 and as will be apparent the entirepositive half-wave of main arc current is obtained. On the other hand,assuming the use of a capacity in the ignition circuit, the ignitionpotential may be left in phase with the main are potential, with theresult of obtaining curves such as shown in Figs. 4.- and 5 according tothe value of the capacity 7 The curves in these figures are lettered thesame as the curves in Figs. 2 and 3 and as will be apparent therefromthe capacity advances the phase of the ignition potential so that itspeak value occurs nearer to the zero value of the 7 operation of thedevice as compared with the ordinary mercury arc rectifier.

Referring to Fig. 6, the same shows a half wave rectifier with amodified arrangement of electrodes. This device comprises a bulb 10having therein a mercury cathode 11, a main anode 12 and an auxiliaryanode 13. The main anode and cathode are similar to those of the deviceshown in Fig. 1,

but the auxiliary ano de in this instance is I ll) might be used inconjunction.

enclosed in a tube 14 of lass or other insulating material, said tuieprojecting into the mercury and having an aperture 15 adjacent thesurface of the mercury to permit the passage of an electrical discharge.Also, in this instance, the ignition potential is supplied to theauxiliary anode and main anode instead of to the auxiliary anode andcathode as in Fig. 1. And with the bulb tilled with inert gas as abovedescribed, this arrangement insures a dense ionization of the gasimmediately over the mercury surface and a continuous path of ionizedgas and vapor from the" cathode to the anode with the result ofincreasing the reliability of ignition.

Referring to Fig. 7, the device shown therein is a modification of thedevice shown in Fig. 6. This device comprises a bulb 16 having a lampbase 17, a mercury cathode 1S electrically connected to the screw shellof said lamp base a main anode 19 and an auxiliary anode 20. Theauxiliary anode is enclosed in a tube 21 of glass or other insulatingmaterial projecting upwardly from the base through the meriury wherebysaid auxiliary anode may be connected to the center contact of the lampbase and as in the previous structure the tube 21 is provided withapertures 22 adjacent the surface of the mercury for the passage of anelectrical discharge. The circuit connections shown in this figure arethe same as in Fig. 6.

Referring to Fig. 8. the same shows a r-o-called double wave rectifier*ith the auto-transformer connections commonly used with this type ofdevice. This device is similar to the device shown in Fig. 7 andcomprises a bulb 25 containing a mercury cathode 26. two main anodes 27and 28 and an auxiliary anode 29 enclosed in an insulating tube 30projecting upwardly from the base of the bulb through the mercury, as inFig. 7. The two main anodes are connectcd to the opposite terminals ofan autotransformer T which is connected across a supply circuit L andthe cathode is connected through a battery 31 representing a load, to anintermediate tap on the auto transformer. The auxiliary anode isconnected to the secondary of a transformer T having a primary windingconnected across the supply circuit L and said secondary winding is alsoconnected to the auxiliary anode 29. A high resistance 32 is included inthe ignition circuit to limit the flow of current therein but it is tobe understood that such resistance might be replaced by a capacity asabove described or the two Further. a switch 33 is provided in thecircuit of the primary winding of the transformer Wherebv the supply ofpotential to the ignition circuit may be terminated after ignition ofthe are as is the usual practice in the case of double wave rectifiers.However, if it be desired to operate the device at currents below thevalue at which the arcs will maintain themselves, switch 33 may be leftclosed and the device will then continue to operate for furnishingrectified currents as low as a few hundredths of an ampere.

Referring to Fig. 9, the same shows two devices 35 and 36 of theconstruction disclosed in Fig. 6, employed as a double wave rectifier tosupply and control a motor M. The motor has aseparately excited fieldwinding F aud an armature A, the latter bein connected on one side tothe cathodes of the devices 35 and 36 in parallel and being connected onthe other side thereof to a center tap of an auto-transformer T suppliedfrom an alternating current circuit L. The devices 35 and 36 have theirmain anodes respectively connected to end taps of the auto-transformer Tand accordingly said devices when ignited will alternately supplyrectified currents to the motor armature in pulses. In this instance theignition potentials for the devices 35 and 36 are su plied bytransformers T and T respectively through thermeo-ionic relays 39 and 40re-,

spectively. The transformers T and T have their primary windingsconnected in.

parallel across line L through a resistance 37 and the transformer T hasits secondary winding connected through a capacity 41 to the auxiliaryanode of device 35, while the transformer T has its secondary windingconnected through a capacity 42 to the auxiliary anode of device 36. Therelays are respectively provided with cathodes 43 and 44 which arerespectively connected to the secondary windings of transformers T 4 andT and which are supplied with heating currents by batteries 45 and 46respectively. Also. the relays are respectively provided with anodes 47and 48 which are respectively connected to the main anodes of devices 35and 36 whereby each transformer will impress a potential upon the mainand auxiliary anodes of its respective rectifying device determinable bythe discharge between the anode and cathode of its respective relay.Further, the relays are respectively provided with grids 49 and 50supplied with potential by a battery 51 subject to the bucking action ofa tachometer 52 driven by motor M. The grids are connected in parallelto the battery 51 and the battery is connected through the armature ofthe tachometer to the cathodes of the two relays in parallel, saidcathodes being bridged by a high resistance 53 and the batteryconnections being made to the symmetrical point of said resistance.

Thus the system will function as follows: Assuming the motor to be inoperation, any variation in the speed thereof will effect a ill) likevariation. in the speed and bucking efl'ect of the tachometer, with theresult of varying thepotential impressed upon the gridcathode circuitsof the relays. If, for exing effect of the tachometer will be increasedand will either increase the negative potential of the rid or reduce thepositive potential thereo depending upon whether the tachometer or thebattery predominates, while if the motor speed decreases a reverseeffect will be obtained and such variations in potential will causeproportional but greatly amplified variations in the discharges throughsaid'relays to decrease or increase the ignition potentials of therectifying devices according to the character and degree of speedvariation of the motor. And such variations in the ignition potentialsof the rectifying devices will tend to correspondingly decrease orincrease the current supplied to the motor whereb said devices willfunction subject to the a oresaid influences of the relays andtachometer to automatically vary the current supplied to the motor tomaintain a substantially constant speed thereof. Thus under suchconditions the current supplied by the rectifying devices is varied byvariations in magnitude of the ignition potential as distinguished fromvariations in the phase relation of the main and ignition potentials, asabove described, and in this connection it may be noted that the currentsupplied to the motor might be varied by changing the phase relation ofthe main and ignition potentials of each device by changing the capacityincluded in the ignition circuits thereof. Further, the current suppliedto the motor might be varied by the resistance 37 which by varying theiotcntial of the primary windings of transformers T and T provide forvariation of the magnitude of the ignition potentials impressed on therectifying devices.

What I claim as new and desire to secure by Letters Patent is:

1. A vapor arc device comprising main arc and ignition electrodesincluding a va-. porablecathode, a vessel to enclose said electrodes, afinely divided surface coating of highly refractory material for saidcathode which readily emits electrons, and an inert gas within saidvessel. ample. themotor speed increases, the buck- 2. In a vapor arcdevice, in combination, a mercury cathode, a surface coating thereforcomprising particles of highly refractory material which readily emitselectrons, a main anode, anvauxiliary anode and a vessel enclosing saidcathode and said anodes and containing an inert gas.

3. The combination with a vapor arc device comprising a vesselcontaining a cathode, a main anode, an auxiliary anode and an inert gas,said anodes being shielded whereby electrical discharges therebetweenare caused to pass in close proximity to said cathode, of a main circuitincluding said cathode and said main anode and an ignition circuitincluding said main and auxiliary anodes.

4. A vapor arc device comprising a vessel containing an inertgas,avaporable cathode within said vessel having a surface coating offine particles of a highly refractory material which readily emitselectrons, and main and auxiliary anodes within said vessel, said anodesbeing shielded from one another whereby electrical dischargestherebetween are caused to pass in close proximity to said cathode.

5. A vapor are device comprising main arc and ignition electrodesincluding a vaporable cathode, a vessel to enclose said electrodes, thearrangement being such that dis- ERWIN R. STOEKLE.

